1. Field of the Invention
The present invention relates to print data processing apparatuses and print data processing methods that carry out processing of print data.
2. Description of the Related Art
In recent years demand has been expanding for variable data printing (hereinafter abbreviated to VDP) in which the data of customers is printed according to their individual needs. In VDP, the unit that expresses the print data of a single customer is referred to as a record. A record is a collection of pages and VDP has a feature of being able to increase the added value of printed matter by carrying out printing using content matched to the customer for each record. For VDP in digital printing, standard VDP languages such as PPML and PDF/VT are defined as page description languages (hereinafter abbreviated to PDL). These VDP languages can classify the images within the print data into reusable objects to be used multiple times and objects for which this is not the case. This is designed so that the image data of reusable objects is cached and the next time when the same object is to be rendered, the cached image data can be reused. By caching and reusing the image data of reusable objects, VDP languages have the advantage of enabling higher speed print processing. For example, PPML, which is one of the VDP languages, is designed so that objects to be reused can be classified as reusable objects and objects other than those can be classified as variable objects, and this enables print data processing according to each of these.
However, depending on the structure of the print data, when printing print data that is described using a VDP language, unfortunately sometimes a much longer time is required than for printing print data that is described using a PDL that is not a VDP language. This type of problem can occur in a case where the print data is of a structure in which identical resource files are processed in a duplicated manner for multiple print objects (sometimes referred to simply as objects) contained within the data. As one example, description is given with FIG. 12 using PPML as the VDP language. With PPML, it is possible to include multiple different print objects described in PDL within the print data as content. In FIG. 12, description is given using an example of a case where PostScript (a registered trademark that is hereinafter abbreviated to PS) is used in the content. With PS, it is possible for print objects to use resources. Types of PS resources include fonts, ProcSets, which are collections of command definitions, forms, and color renderings that represent color profile settings. Suppose that there are four PS objects within a set of PPML print data, and that an identical PS font file 1 is duplicated and independently described in each of the PS objects. Unfortunately in this case, when processing the PPML print data, the process is performed for the number of times that the PS font file 1 is described, namely four times. In contrast to this, FIG. 13 shows an example of a case where the same content is described as PS print data rather than PPML data.
In FIG. 13, processing can be achieved with the PS font file 1 being described only once the first time it is used. Thus, the PS font file 1 is processed more times and the processing time becomes undesirably longer in the case of using PPML. Although it is a feature of print data described in a VDP language that it is designed to enable shorter processing times, with this type of print data, a VDP language instead requires longer processing times.
A conventional technique described in Japanese Patent Laid-Open No. 2008-271098 is available as a means for solving this issue. This patent literature describes a document merging method in which, when merging different digital documents, the merged file size can be kept small by performing the merging after deleting common resources. When this conventional technique is applied to print data processing, it is possible not only to keep the merged file size small, but also to shorten the processing time of the print data.
However, the above-described conventional technique can only be applied in a case where print objects that use same resources are described successively within the print data. Since print objects targeted for shortening processing times are not necessarily described successively within the print data, a more widely applicable method is desired for further increasing the efficiency of print data processing.